Abstract: The ϕ280 mm large size blank of domestic EA4T steel was selected as the equivalent axle, and the heat treatment pre-test of water quenching for 900 ℃×5 h and tempering at different temperatures (595,610,650 ℃) for 6 h and water cooling was carried out. The microstructure and mechanical properties of the surface layer, 1/2 radius position and core of the axle were anlyzed to obtain the proper quenching and tempering heat treatment process, and the field verification of the heat treatment process was carried out on ϕ256 mm EA4T steel axle. The results show that the tensile strength of different areas after 595 ℃ water cooling tempering and the surface layer after 610 ℃ water cooling tempering for the equivalent axle was higher than standard requirements of EN 13261: 2009. The strength, percentage elongation after fracture, percentage reduction of area, and longitudinal and transverse impact toughness after water cooled tempering at 650 ℃ met the standard requirements of EN 13261:2009, and the microstructure was basically tempered martensite/bainite. The quenching and tempering heat treatment process for EA4T steel axle was determined as 900 ℃×5 h water quenching and 650 ℃×6 h water cooling tempering. After ϕ256 mm EA4T steel axle was heat-treated by the above process, the mechanical properties and microstructure of the surface, 1/2 radius position and core of the axle all met the standard requirements of EN 13261:2009. After sampling in different areas and stretching, ductile fracture occurred, and the fracture was composed of fiber regions and shear lips with the fiber regions showing dimpling morphology.